CN3795

CN3795 is a PWM step-down multi-cell battery charger management IC that can be powered by a solar panel, suitable for charging management of single-cell or multi-cell lithium-ion, LiFePO₄, or lithium titanate batteries. CN3795 features trickle, constant current, and constant voltage charging modes. The constant current charging current is set by the current sense resistor R_CS connected between the CSP pin and the BAT pin. The constant voltage charging voltage is set by the feedback resistors connected to the FB pin. When the VCC pin voltage exceeds the UVLO threshold and is greater than the battery voltage, CN3795 operates normally. If the battery voltage falls below the trickle charge threshold, the charger automatically enters trickle charge mode, in which the charging current is 17.5% of the set constant current. When the battery voltage exceeds the trickle charge threshold, the charger enters constant current mode, where the charging current is determined by an internal 1.20 mV reference voltage and an external resistor R_CS, i.e., the charging current equals 120mV/R_CS. As the battery voltage continues to rise and approaches the constant voltage charging level, the charger enters constant voltage mode and the charging current gradually decreases. During charging, the internal transistor of the open-drain output pin conducts and pulls the output low to indicate the charging status. When the charging current drops to 16% of the constant current setting, charging is complete and the DRV pin outputs a high level. The internal transistor of the open-drain output pin turns off, and the output becomes high-impedance to indicate the end-of-charge state. In the end-of-charge state, disconnecting and then reconnecting the input power will initiate a new charge cycle; if the charging current rises above the recharge threshold again, a new charge cycle will also start automatically. CN3795 can be powered by a solar panel and features maximum power point tracking (MPPT) for solar panels. The solar panel maximum power point voltage is fed back to the MPPT pin through a resistive voltage divider. In MPPT mode, the MPPT pin voltage is regulated to 1.205V (typical). When the input voltage drops, CN3795 automatically enters sleep mode and the internal circuitry is shut down. CN3795 also incorporates an overvoltage comparator. When the BAT pin voltage rises due to load changes or sudden battery removal, if the BAT pin voltage rises to 1.07 times the constant voltage charging level, the overvoltage comparator activates and turns off the external P-channel MOSFET, temporarily halting charging until the BAT pin voltage falls back below 1.02 times the constant voltage charging level.

Applications

• Handheld devices
• Emergency lighting
• Backup battery applications
• Portable industrial and medical instruments
• Power tools
• Li-ion, LiFePO₄, and Li₄Ti₅O₁₂ battery charging

Key features

• Solar panel MPPT
• Full charge management for single or multi-cell lithium-ion, LiFePO₄, or lithium titanate batteries
• Wide input voltage range: 6.6V to 30V
• Operates as a regulated voltage source when no battery is connected
• Charge current up to 4A
• PWM switching frequency: 310KHz
• Constant voltage set by external resistor
• Constant current set by external resistor
• Trickle charging for deeply discharged batteries
• Automatic recharge function
• Charge status indication
• Soft-start function
• Battery overvoltage protection
• Operating temperature range: -40°C to +85°C
• 10-pin SSOP package
• Lead-free, RoHS compliant, halogen-free